1. Field of the Invention
This invention relates to a robot arm coupling device that attaches and detaches various tools to a robot arm of a polyarticular robot, or attaches and detaches a chuck etc. to upper and lower arms, a pivot arm of a molded article takeoff device.
2. Description of the Related Art
As a coupling device capable of attaching and detaching a tool etc. to and from a robot arm, as disclosed in Jpn. Pat. Appln. Laid-Open Publication No. 4-63688, there is a known device that includes a master plate (inner assembly) which is attached to a robot arm, a tool plate (outer assembly) to which a tool etc. is attached, and locking means that couples and locks these plates.
The locking means of the device includes a cam member in the form of a disc which is slidably supported on the master plate between the locking position and the unlocking position, a plurality of ball members which are arranged around the cam member, and are slidably supported in the master plate in a direction substantially perpendicular to the sliding direction of the cam member, and a ball receiver in the form of a ring which is arranged in the tool plate, and is engaged with the ball members such that the both plates are coupled to be retained when the cam member is shifted to the locking position, and the cam member has an arm side tapered surface (cam surface) formed around the outer circumference thereof, while the ball receiver has a tool side tapered surface (cam surface) formed around the inner circumference thereof, which tool side tapered surface inclines in the reverse direction with respect to the arm side tapered surface.
The locking means mutually couples the master plate and the tool plate firmly, with the cam member located at the locking position, and with the ball members pressed by the arm side tapered surface to be made to abut on the tool side tapered surface.
Furthermore, the locking means disclosed in Jpn. Pat. Appln. Laid-Open Publication No. 4-63688 releases the pressing action by the arm side tapered surface toward the ball members and releases the engagement of the ball members with the tool side tapered surface when the cam member is shifted to the unlocking position, making the tool plate detachable from the master plate.
However, in unlocking the master plate and tool plate, when detaching the tool plate from the master plate by only releasing the pressing action by the ball members toward the tool side tapered surface, it is necessary to control the posture of the master plate and tool plate such that the coupling surface thereof is set horizontal so as to make the tool plate separate from the master plate due to the own weight of the tool plate.
Accordingly, in a robot or in the working environment which cannot control the posture such that the coupling surface of the master plate and tool plate is set horizontal, the tool plate cannot be made to automatically separate by itself. That is, in a robot arm in which the coupling surface of the master plate and tool plate is directed in a direction other than the horizontal direction, the worker has to perform the exchange work to forcibly pull out and detach the tool plate from the master plate, which plates are unlocked. At this time, there is a problem that the exchange work is troublesome and time-consuming.